Treating metal with a composition including a chlorinated lower hydrocarbon and an organic phosphate complex



United States Patent 3,249,471 TREATING METAL WITH A COMPOSITION IN- CLUDING A CHLORINATED LOWER HYDRO- CARBON AND AN ORGANIC PHOSPHATE COM- PLEX William A. Higgins, Gates Mills, Ohio, assignor to The Lubrizol Corporation, Wickliffe, Ohio, a corporation of Ohio No Drawing. Filed Nov. 9, 1962, Ser. No. 236,714

Claims. (Cl. 1486.15)

The present invention relates to an improved method of forming an adherent, protective coating on a metal article. In a more particular sense, it relates to a method for protecting ferrous metal articles against the ravages of corrosion.

The corrosion of metal surfaces is of obvious economic significance in many industrial applications and, as a consequence, the inhibition of such corrosion is a matter of prime consideration. It is particularly significant to users of steel and other ferrous alloys. The corrosion of such ferrous metal alloys is largely a matter of rust formation, which in turn involves the overall conversion of the free metal to its oxide.

The theory which best explains such oxidation of ferrous metal surfaces postulates the essential presence of both water and oxygen. Even minute traces of moisture are sutlicient, according to this theory, to induce the dissolution of iron therein and the formation of ferrous hydroxide until the water becomes saturated with ferrous ions. The presence of oxygen causes oxidation of the resulting ferrous hydroxide to ferric hydroxide, which then settles out of solution and is ultimately converted to ferric oxide or rust.

The above sequence of reactions can be prevented, or at least in large measure inhibited, by relatively impermeable coatings which have the effect of excluding moisture and/or oxygen from contact with the ferrous metal surface. Such coatings are, of course, subject to abrasion, flexing, and other forms of physical deformation and to the extent that these coatings are penetrated or otherwise harmed by such influences they become less effective for the desired purpose. It is important then, that such coatings provide protection for all or most of the ferrous metal surface. A satisfactory protective coating composition, then, should have the ability to withstand corrosive, humid atmospheres, abrasion, and substantial deformation or rupture upon impact so that the protective film is maintained on the metal surface. It should also function well as a base upon which one can apply a subsequent decorative topcoat of a known, siccative organic coating composition such as paint, enamel, lacquer, synthetic resins, etc.

Phosphate coatings have been widely employed for this purpose, i.e., to provide an adherent protective coating which also serves as an excellent base for a topcoat of paint, enamel, or the like. Such phosphate coatings are generally formed on a metal article by means of aqueous solutions which contain small amounts of the phosphate ion and, optionally certain auxiliary ions, including metallic ions such as sodium, manganese, zinc, cadmium, iron, copper, lead, nickel, cobalt, and antimony ions, and nonmetallic ions such as ammonium, chloride, bromide, fluoride, nitrate, and chlorate ions. These auxiliary ions modify the character of the phosphate coating and adapt it for a wide variety of applications. The preparation and use of aqueous phosphating solutions is well-known in the metal finishing art as shown 'by US. Patents 1,206,075; 1,247,668; 1,305,331; 1,485,025; 1,610,362; 1,980,518; 2,001,754; and 2,875,111.

Aqueous phosphating solutions are generally prepared by dissolving in water small amounts of phosphoric acid and, optionally, at least one metal salt such as a nitrate, phosphate, nitrite, sulfate, fluoride, or bromide of sodium, manganese, zinc, cadmium, iron, nickel, copper, lead, or antimony. Ordinarily an oxidizing agent such as sodium chlorate, potassium perborate, sodium nitrate, ammonium nitrate, sodium chlorite, potassium perchlorate, or hydrogen peroxide is included in the phosphating solution to depolarize the metal surface being treated and therefore increase the rate at which thephosphate coating is formed on the metal surface. Other auxiliary agents such as anti-sludging agents, coloring agents, and metal cleansing agents may also be incorporated in the phosphating solution. One common type of commercial phosphating bath contains zinc ion, phosphate ion, and a depolarizing agent, which bath is made by dissolving small amounts of zinc dihydrogenphosphate, sodium nitrate, and phosphoric acid in water.

More recently, workers in the field of protective coatings have used non-aqueous phosphating solutions to avoid disadvantages which generally attend the use of aqueous phosphating solutions such as poor chemical efficiency with respect to utilization of the active ions, sludging, failure to wet and coat certain metallic surfaces completely, etc. These non-aqueous phosphating solutions generally consist of a hydrocarbon or chlorinated hydrocarbon solvent containing dissolved or dispersed phosphoric acid. Thus, for example, one known nonaqueous phosphating solution consists of a chlorinated hydrocarbon solvent containing monoand di-alkyl acid phosphates and orthophosphoric acid. Another such phosphating solution consists of a chlorinated hydrocarbon solvent containing a minor proportion of orthophosphoric acid held in solution or suspension by means-of a sorbitan ester. Still other solutions consist principally of an organic solvent, orthophosphoric a-cid, metal acid phosphates, and detergents and emulsifiers to maintain the inorganic ingredients in a fine state of suspension in the solvent. Although such non-aqueous phosphating solutions have obviated some of the shortcomings of aqueous phosphating solutions, they have not found wide application in the protective coating field, principally because the coatings formed thereby are deficient in corrosion inhibiting power.

It is, therefore, an object of the present invention to provide an improved method of forming a protective coating on a metal article.

Another object is to provide a metallic article having on the surface thereof a coating which serves as an excellent base for the subsequent reception of a. topcoat of a known, siccative organic coating composition.

These and other objects of the invention are realized by means of an improved method of forming an adherent, protective coating on a metal article which comprises:

(A) Cleaning said article by contacting it'with the vapors of a boiling, chlorinated lower hydrocarbon.

(B) Immersing said article in a liquid, organic coating composition containing as essential ingredients a chlorinated lower hydrocarbon and an organic phosphate complex and being maintained at about the boiling point of said chlorinated lower hydrocarbon, said organic phosphate complex having been prepared by the process which comprises mixing one mole of phosphorus pentoxide, from about 0.2 to about 12.5 moles of a copolymer of allylalcohol and a styrene, and from about 0.3 to about 5.0 moles of an alkylphenol, and heating said mixture at a temperature within the range from about C. to about C., and

(C) Removing said article from the liquid, organic coating composition of (B), whereupon the chlorinated lower hydrocarbon evaporates and a film of the organic phosphate complex is deposited on the article.

protecting metal articles, especially ferrous metal articles,-

against the ravages of corrosion. Its effectiveness is believed to be due at least in part to its superior bonding or adhesion characteristics with respect to the metallic surface.

STEP A As noted above, this step involves cleaning the metal article by contacting it with the hot vapors of a boiling, chlorinated lower hydrocarbon. The vapors of the chlorinated lower hydrocarbon condense on the cool metal article. The liquid chlorinated lower hydrocarbon thus condensed on the metallic surface of the article removes any dirt or grease and the contaminated liquid drops by gravity from the article. Any of the various chlorinated lower alkanes or alkenes containing from 1 to about carbon atoms and from 1 to about 6 chlorine atoms are suitable for the purpose such as, e.g., carbontetrachloride, 1,2-dichloroethane, 1,1 dichloroethane, 1,1,1 trichloroethane, 1,1,2-trichloroethane', 1,1,2,2-tetrachloroethane, pentachloroethane, 1,1-dichloropropane, 1,1 -dichloro-2- methyl-propane, 1,4-dichloro-2-methyl-butane, 2,3-dichlor0 2 methyl-butane, trichloroethylene, tetrachloroethylene, etc. Generally the chlorinated lower hydrocarbon should boil within the range from about 60 C. to about 150 C. In most cases the chlorinated lower hydrocarbon will be a chlorinated ethane or chlorinated ethylene, with a particular preference being expressed for trichloroethylone and tetrachloroethylene.

There is nothing'especially critical about the cleaning step. The metal article to be cleaned is simply contacted with the vapors of the boiling chlorinated lower hydrocarbon for a sufiicient time to allow the condensation of the with either the copolymer or the alkylphenol, heat the mass at about 75-150 C., add the remaining reactant, and then continue heating.

Ordinarily the reaction is carried out in a solvent and the solvent then removed, if desired, by distillation when the reaction is completed. Suitable solvents for this reaction include, e.g.,-xylene, benzene, cyclohexane, chlorobenzene, ethylene dichloride, and dioxane. Other inert, relatively volatile solvents may also be used. The reaction may also be carried out in the absence of a solvent. If desired, the essential ingredient of the liquid organic coating composition, viz., the chlorinated lower hydrocarbon, may be used as a solvent for the reaction.

The reaction of the process appears to involve first a reaction between phosphorus pentoxide and the copolymer of allylalcohol and a styrene, followed then by reaction of this intermediate product with the alkylphenol. Presumably this latter reaction is a transesterification. The reaction mixture is at first cloudy and viscous, but as the reaction proceeds the cloudiness and high viscosity disappear and the final product is a relatively clear solution. The optimum reaction time is about 4 to 6 hours, although a suitable product can be obtained at any point within a period from about 1 to about 10 or more hours.

The copolymer of allylalcohol and a styrene is preferably a low molecular weight copolymer prepared from an approximately equimolar mixture of the two monomers,

vapors thereon. Usually a few, say 2 to 10 minutes is adequate. Of course, a longer time can be used but is generally neither necessary nor desirable.

STEP B In this step, the cleaned article from step A is immersed in the hot, liquid organic coating composition of the invention, which contains as essential ingredients a chlorinated lower hydrocarbon (such as described in Step A) and an organic phosphate complex in a weight ratio from about 0.5:1 to about 20:1, more often from about 1:1 to about 9:1. 1n order to accomplish the objects of this invention, the organic coating composition must be maintained at or near the boiling point or the chlorinated lower hydrocarbon. Under these conditions, the temperature of the article immersed in the coating composition approaches the boiling point of the chlorinated lower hydrocarbon. As in .Step A, the chlorinated lower hydrocarbon will generally be a chlorinated ethane or chlorinated ethylene, with a particular preference being expressed for trichloroethylene and tetrachloroethylene.

The organic phosphate complex used in the coating composition of this invention is made, as indicated previously, by the reaction of phosphorus pentoxide with an alkyl phenol and a copolymer of allylalcohol and a styforming a part of the present specification.

In brief, this ingredient is prepared by mixing one mole of phosphorus pentoxide, from about 0.2 to about 12.5

moles'of a copolymer of allylacohol and a styrene, and from about 0.3 to about 5.0 moles of an alkylphenol, and

' heating said mixture at a temperature within the range I from about 75 C. to about 150 C. In some instances it is desirable to carry out the process in stepwise fashion. For example, one may first mix the phosphorus pentoxide although the mole ratio of the two monomers may vary broadly from about 1:10 to about 10:1. The molecular weight of the copolymer is generally within the range from about 750 to about 1500, preferably about 1,100- 1,150. The styrene monomer may be styrene itself, and most usually it is, or it maybe any of thevarious substituted styrenes such as monochloro-styrene, alkyl-substituted styrenes, and alpha-substituted styrenes in which latter the substituent is an alkyl group, preferably a methyl group. A particular preference is expressed for a copolymer of approximately equimolar amounts of allylalcohol and styrene having an average molecular weight of about 1,100-1,150. Such a copolymer is available commercially under the trade designation Polyol X-450. Similar copolymers of lesser or greater average molecular weight are also available commercially, such as Monsanto RJ which has an average molecular weight of about 1,580.

The alkylphenol reactant may be either a mono-alkyl or a poly-alkyl phenol. The alkyl groups may be of any size, ranging from methyl up to alkyl groups derived from olefin polymers having molecular weights as high as 50,000 or more. Preferably the alkylphenol is a mono-alkyl phenol in which the alkyl group contains from 1 to about 30 carbon atoms, preferably about 4 carbon atoms. Typical examples of useful alkylphenols include, e.g., ortho, meta, and paracresols; ortho, meta, and para-ethylphenols; ortho, para-diethylphenol; para-isopropyl phenol, para-tertiary butylphenol, para-tertiary amylphenol, heptylphenol, diisobutylphenol, n-decylphenol, wa alkylated alpha-naphthol, Wax-alkylated phenol, and polyisobutenesubstituted phenol in which the polyisobutene substituent contains from 20 to about 80 carbon atoms. The alkylphenol may also contain substituent groups such as chloro, fluoro, nitro, alkoxy, sulfide, nitroso, etc. In certain instances, it is desirable to use polyhydric phenols and their substitution products such as resorcinol, catechol, pyrocatechol, and the corresponding alkylated resorcinols, alkylated catechols, etc.

The process for forming the organic phosphate complex used in the method of this invention is carried out simply by mixing the specified reactants, preferably with a solvent, and heating the resulting solution ata temperature Within the range from about 75 C. to about C. until the reaction is complete. As indicated earlier, the first stages of the overall reaction produce a cloudy, thickened reaction mixture and as the reaction proceeds this is changed to a relatively clear, non-viscous solution. Several illustrative examples follow. The acid Nos. are determined according to ASTM procedure D974-55T using the stated end point indicator. All parts and percentages are by weight unless otherwise indicated.

Example 1 i The reaction mixture is stirred throughout this period and water of reaction is removed by means of a side-arm watertrap. At the end of this time the xylene is removed by distillation to yield a plastic, non-viscous mass. This residue, while still hot, i.e., at about 100 C., is diluted with 824 parts of trichloroethylene. The product, a 65% solution of the organic phosphate complex in trichloroethylene, shows the following analyses:

Percent phosphorus 1.16 Acid No. (phenolphthalein indicator) 226 Example 2 A mixture of 313 parts (0.284 mole) of Polyol X450, 314 parts (0.786 mole) of mono-(polyisobutene-substituted) phenol wherein the polyisobutene substituent contains an average of about 22 carbon atoms, 31 parts (0.218 mole) of phosphorus pentoxide, and 660 parts of xylene is heated to the reflux temperature and maintained at this temperature for 6 hours while water is removed by means of a side-arm water-trap. Substantially all of the xylene is removed by distillation of the mass at 140 C./ 20 mm. Hg and then the residue is diluted with 350 parts of trichloroethylene.- The product, a 65% solution of the organic phosphate complex in trichloroethylene,

shows the following analyses:

Percent phosphorus 1.35

Acid No. (bromphenol blue indicator) 16.7

Example 3 800 parts (0.73 mole) of Polyol X-450, 272 parts (1.66 moles) of paratertiary amylphenol, 80 parts (0.57 mole) of phosphorus pentoxide, and 1.148 parts of xylene solvent are introduced into a reaction vessel fitted with a stirrer and a side-arm water-tray. The whole is heated at the reflux temperature (132l40 C.) for 6 hours while the water of reaction is removed by means of the side-arm water-trap. The pressure on the reaction vessel is then lowered to 30 mm. Hg to remove the xylene solvent; After all of the xylene solvent has been removed, 616 parts of trichloroethylene is added. The resulting product, a 65% solution of the organic phosphate complex in trichloroethylene, shows the following analyses: Percent phosphorus, 2.0.

Example 4 1,562 parts of xylene solvent is charged to a reactor and heated to 90 C. 1,096 parts (0.996 mole) of Polyol X-450, 372 parts (2.5 moles) of para-tertiary amylphenol, and 110 parts (0.775 mole) of phosphorus pentoxide are added thereto and the whole is stirred under reflux for 6 hours at l34136 C. 18 parts of water is removed in the side-arm water-trap. 600 parts of the xylene solution thus obtained is stripped of xylene at 137 C./ 28 mm. Hg. The solvent-free organic phosphate complex thus obtained (300 parts) is mixed with 300 parts of trichloroethylene at 80 C. The product, a 50% solution of the organic phosphate complex in trichloroethylene, is found to-have the following analyses:

Percent phosphorus 1.61 Acid No. (bromphenol blue) 12.8

6 Additional examples of organic phosphate complexes useful herein are shown in Table I. They are prepared in the same manner set forth in Example 1 using the indicated quantities of reagents.

TAB LE I Moles of the indicated starting materials to be employed Alkylphenol Phosphorus x-iso Identity 7 Parai-tertiary amylphenol. o

oooooo marrow- 9 0 STEP C As indicated earlier, this step involves the removal of the metal article from the hot, liquid coating composition. Upon removal of the article from the coating composition, the chlorinated lower hydrocarbon evaporates quickly, in fact almost instantaneously, from the layer of coating composition on the surface of the article, de-

positing an adherent film of the organic phosphate complex thereon. The thus-coated article is ready for use either as such or to receive a decorative topcoat of enamel, lacquer, etc. If desired, the removal of the article from the hot coating composition may be accomplished in the manner described in Borushko US. Patent 2,783,165, which permits the condensation and re-use of the chlorinated lower hydrocarbon which has volatilized from the coating composition.

The following examples are presented to set forth specific modes of carrying out the method of the present invention. Such examples are given for purposes of illus- .tration only and are not to be construed as limiting the scope of the invention, except as the latter is defined by the appended claims. Unless otherwise stated, all parts and percentages are by weight.

Example I Six 4-inch by 8-inch panels of ZO-gauge SAE 1020 cold-rolled steel were cleaned by exposing them to the vapors of boiling trichloroethylene for 5 minutes. The six cleaned panels were then immersed, respectively, in six different hot :3 C.) coating compositions of the invention for one minute. Upon removal of the panels 0 from the coating composition, the trichloroethylene volatilized quickly and deposited a film of the organic phosphate complex on the metallic surfaces. coating of these panels are set forth in Table II.

Two sets of six steel panels each were provided, respectively, with a zinc phosphate coating (panels B -B and an iron phosphate coating (panels C C by means of proprietary aqueous phosphating solutions.

These control panels were then compared with the panels of the invention in a Salt Fog Corrosion test. The apparatus employed for this test is described in ASTM Procedure B1l757T. It consists of a chamber in which wipe-pane Details on the corrosion inhibiting and adhesive characteristics of protective coatings.

The Salt Fog Corrosion test referred to previously was employed. In the present instance, the panels subjected TABLE III.-SALT FOG CORROSION TEST Iron Phosphated Control Panel of the Invention; P l R k ane; emar s Zinc Phosphated Control Panel; Remarks Remarks An; spotty, very light rust B6; light red rust overall A; spotty yellowish tinge but Ca; heavy red rust overall. B light red rust overall C heavy red rust overall.

4 Aggp t ty y llowish tinge but B light red rust overall O4; heavy red rust overall. 8 Ag g t ty fiirange tinge but no Bel light red rust overall 0;; heavy redrust overall. 10 Ai l ig lilz ied rust on panel edges 13;; light red rust overall Oi; heavy red rust overall. 12 Ag ii rustgv; B1; light red rust overall C1; heavy red rust overall.

It will'be noted that each of the six panels coated in accordance with the method of this invention were superior to panels provided with a known zinc phosphate or iron phosphate coating. Best results were obtained on panels of the invention having a dry coating weight within the range of 500-2000 mg./sq. ft. of surface area.

Example 11 This experiment was carried out to determine the effectiveness of the method of this invention with respect to providing a base for the subsequent application of a known, siccative organic coating composition.

Three steel panels of the type described previously were cleaned by exposing them to the vapors of boiling tetrachloroethylene for 4 minutes. The cleaned panels were immersed for 5 minutes in a hot (l70180 F.) liquid coating composition of the invention prepared by diluting the product of Example 4 with sufficient trichloroethylene to yield a 20.5% solution of the organic phosphate complex in trichloroethylene. After 5 minutes, the panels were removed and the trichloroethylene volatilized quickly, depositing a film of the organic phosphate complex on the metallic surfaces. The'thus-coated panels were sprayed with a good, commercial, urea-modified white alkyd baking enamel and then baked in an oven for 15 minutes at 325 F. For convenient identification, these panels of the present invention were identified as Group D panels.

Another set of three steel panels was prepared in the same manner set forth above except that a known, prosolution contains trichloroethylene, alkyl acid phosphates,

orthophosphoric acid, and an emulsifier. For convenient identification these control panels were identified as Group E panels.

Another set of three steel panels was prepared as set forth in the previous paragraph, this time using a second known, proprietary non-aqueous phosphating solution.

to the test were scribed with a pointed steel instrument so as to yield a vertical score beginning one inch from the top of the panel and ending one inch from the bottom thereof. After the panels had been exposed to the salt fog for hours, they were removed from the test chamber and scraped with a putty knife to remove any non-adherent coating. The percent of the total panel area still covered by an intact film was measured and reported in Table IV as percent of film intact.

Panels from each group were also subjected to a reverse impact test to determine the adhesion characteristics of the coatings under sudden impact. This test employs the Gardner Variable Impact tester'in which the test panel is placed horizontally over a firinch diameter hole in a base plate. A 2-pound steel rod, rounded at the bottom, is dropped from specified heights (in increments of one-inch) through a graduated tube so that it strikes the test panel over the /s-inch hole in the base plate. The height from which the steel rod is dropped on the test panel is increased until the panel dimples and causes the paint film to flake or crack. The greatest height from which the steel rod is dropped and leaves the paint. film unruptured is taken as a measure of the resistance of the coating composition to sudden impact. The test results are expressed in terms of inch-pounds, i.e., a value calculated by multipling the height in inches by the weight in pounds of the steel rod. The particular equipment used in this case is capable of measuring impact resistance up to inch-pounds. Either side of the impacted test panel may be inspected for failure of the paint film, but the convex side of the dimple produces failure first. All of the test data reported in Table IV are based upon an inspection of the convex side of the dimple on the test panels,,thus the name Reverse Impact test is derived.

Panels from each group were also subjected to a combined flexing-water soak test designated as a Conical Mandrel-Water Immersion test. The apparatus employed in this test is described in ASTM Procedure D522- 41. In brief, a coated panel is placed in contact with a steel cone of fixed size and shape and then bent along its 4-inch dimension. The bentpanel is then placed in a beaker filled with water to a depth of about 4 inches in a manner such that the unbent portion of the panel is immersed in the water and the bent portion is suspended in the vapor space above the surface of the water. The

water is heated to 160 F. and the panel is allowed to remain in the beaker for 16 hours. Upon removal of the panel, any cracking of the coating on the bent portion thereof is examined with respect to the severity of such cracking and the length in millimeters of the longest crack. These test data are likewise reported in Table IV below.

TABLE 1V.CORROSION AND ADHESION TESTS Salt Fog Corrosion Test, percent of film intact Reverse Impact Test, Inch-pounds Panel Group Tested to failure Severity of cracking Conical Mandrel-Water Immersion Test Longest crack, Length in. mm.

D (of the invention) 60 E 63 5 Heavy cracking F 38 5 d0 Very light, fine cracks-..

It will be noted that the panels prepared in accordance with the method of this invention were superior to the control panels of Groups E, F, and G in each of the three tests conducted.

In addition to its utility as a means for inhibiting the corrosion of ferrous metals, the method of this invention is also useful in protecting non-ferrous metals such as aluminum, magnesium, copper, brass, bronze, white metal, etc., against corrosion. It is likewise useful to provide protection for galvanized ferrous surfaces and plated ferrous surfaces such as copper-plated, nickel-plated, and cadmium-plated surfaces. It is also useful to provide protection for chromated aluminum or zinc surfaces, i.e., aluminum or zinc surfaces which have been treated with a solution, generally aqueous, of chromic acid and/or a derivative thereof such as a metal chromate or dichromate, an amine chromate, ammonium chromate, etc.

What is claimed is:

1. An improved method of forming an adherent, protective coating on a metal article which comprises:

(A) cleaning said article by contacting it with the vapors of a boiling, chlorinated lower hydrocarbon,

(B) immersing said article in a liquid, organic coating composition containing as essential ingredients a chlorinated lower hydrocarbon andan organic phosphate complex in the weight ratio of from about 0.5 :1 to 20:1 and being maintained at about ,the boiling point of said chlorinated lower hydrocarbon, said organic phosphate complex having been prepared by the process which comprises mixing one mole of phosphorus pentoxide, from about 0.2 to about 12.5 moles of a copolymer of allyl alcohol and a styrene, and from about 0.3 to about 5.0 moles of an alkylphenol, and heating said mixture at a temperature within the range from about 75 C. to about 150 C., and

(C) removing said article from the liquid organic coating composition of (B), whereupon the chlorinated lower hydrocarbon evaporates and a film of the organic phosphate complex is deposited on the article.

further in that the copolymer of (B) has a molecular weight in the range of about 1,1001,l50 and a ratio of the monomers allyl alcohol and styrene of about 1:1. 6. A method in accordance with claim 1 characterized further in that the alkylphenol of (B) is an amylphenol.

7. A method in accordance with claim 1 characterized further in that the alkylphenol of (B) is para-tertiary amylphenol.

8. A method in accordance with claim 1 characterized further in that the relative proportions by weight of the chlorinated lower hydrocarbon and the organic phosphate complex in the coating composition of (B) are from about 1:1 to about 9:1.

9. A method in accordance with claim 5 characterized further in that the chlorinated lower hydrocarbon of (A) and (B) is a chlorinated ethylene and the alkylphenol of (B) is para-tertiary amylphenol.

10. A metal article which has been provided with an adherent, protective coating in accordance with the meth- 0d of claim 1.

References Cited by the Examiner UNITED STATES PATENTS 8/1962 Fullhart et al. 148-6.15 5/1964 Higgins 148-6.27X 

1. AN IMPROVED METHOD OF FORMING AN ADHERENT, PROTECTIVE COATING ON A METAL ARTICLE WHICH COMPRISES: (A) CLEANING SAID ARTICLE BY CONTACTING IT WITH THE VAPORS OF A BOILING, CHLORINATED LOWER HYDROCARBON, (B) IMMERSING SAID ARTICLE IN A LIQUID, ORGANIC COATING COMPOSITION CONTAINING AS ESSENTIAL INGREDIENTS A CHLORINATED LOWER HYDROCARBON AND AN ORGANIC PHOSPHATE COMPLEX IN THE WEIGHT RATIO OF FROM ABOUT 0.5:1 TO 20:1 AND BEING MAINTAINED AT ABOUT THE BOILING POINT OF SAID CHLORINATED LOWER HYDROCARBON, SAID ORGANIC PHOSPHATE COMPLEX HAVING BEEN PREPARED BY THE PROCESS WHICH COMPRISES MIXING ONE MOLE OF PHOSPHORUS PENTOXIDE, FROM ABOUT 0.2 TO ABOUT 12.5 MOLES OF A COPOLYMER OF ALLYL ALCOHOL AND A STYRENE, AND FROM ABOUT 0.3 TO ABOUT 5.0 MOLES OF AN ALKYLPHENOL, AND HEATING SAID MIXTURE AT A TEMPERATURE WITHIN THE RANGE FROM ABOUT 75*C. TO ABOUT 150*C., AND (C) REMOVING SAID ARTICLE FROM THE LIQUID ORGANIC COATING COMPOSITION OF (B), WHEREUPON THECHLORINATED LOWER HYDROCARBON EVAPORATES AND A FILM OF THE ORGANIC PHOSPHATE COMPLEX IS DEPOSITED ON THE ARTICLE. 